Rectifier transformer



p i 1935. H. WINOGRAD 1,999,746

RECTIFIER TRANSFORMER Filed Oct. 25, 1953 Patented Apr. 30.1935 f Q 1,999,746

* UN TED TAT P TE OF RECTIFIER TRANSFORMER 1' Harold- Winograd, Milwaukee, Wis., assignor to Allis-Chalmers Manufacturing Company, Milwaukee; Wis a corporation of Delaware inst ntia ion, 25, 1935, Serial Not 695,157 g i '1 Claims. '(01. 175 -363) This-invention relatesto improvements in elecat normal value during abnormaloperating contric current converting systems, andz more par ditions tending to disturb suchmagnetization. ticularlyto means for insuring the normal opera- Another object of the present invention is to tion of. an interphase transformer forming apart provide an electric current converting system em- 5 of such system .even"when'operating conditions ploying an interphase transformer in which the .5

tend to disturb suchoperationy: I; 1 interphase transformer remains operative when In electric current rectifying systems; use is the currentflowingtherethrough is insufficientto frequentlymmade of interphase transformers, magnetize the core thereof. which are auto-transformers connectingaidirect Objects and advantages other than those above current line with-aplurality of supply circuits described will be apparent from the following 10. having the same average voltage butpresenting description when read in connection with the alternating currentvoltage components which are accompa y g drawing, in which: not in phase coincidence. Suchinterphase trans F g: 1 diagrammatieallyillustrates One embodiformers cause thesimultaneous flow of current at ment "of the Present invention in which e'siX' every instant in the several supply. circuits b t phase alternating current irectifier is supplied 15 do not control the current distribution .therebefrom a h 'ph e lin and tween. The interphase transformers are designed schematically us the preferred 1 predetermined current djstributiontwhich construction oftthe interphase transformer utimaintained under normal operating conditions as liZed in theisystem illustrated in 20 a result of the connection utilized, but become Referring e'p a y e drawing by 20 ineffective when such current di t ibuti i 11 characters of reference,'reference numeral 6 desturbed. Such disturbance may result from such igrlates p yp l n in urr n l n causesas the presence of certain harmonics in gized to y desired Voltage at y Suitable the voltages tith supply line, fron'idissymmeqn a d' herein represented a a ee phase triesin the reactances of the transformer windline solely for t r as hat su yp of line 25 ings or from abnormal operating conditions withis most frequently utilized in P a c L e 5 is in the rectifier. The result of such disturbances connected with the p y winding 1 0f pp y is thatthe core of the interphase transformer retransformer p d w two secondary d-- ceives a direct current flux component bringing ings 9 and 9. Eaeh'seeendary windingreomprises such core to magnetic saturation, thereby render I -p u ailty of p a displaced seetiens n t d 30 ing the interphase transformer inefiective and to'form a neutral point and severallyconnected the output voltage of the system departs from the with the anodes l Of an electron discharge denormal value thereof. i e i vice l2 havinga cathode l3. Device I2 is repre- By providing means for maintaining, with e sented as being of the metallic cathode arcing coreof the interphase transformer, an alternating type ut may be of a y other p p a le as a 35 current flux component ofnormal value even o alternating current rectifier such as the vacuum, occurrence f dir t current magnetization the contact and electrolytic types. Cathode'l3 is conoperation of th interphase tran fo'rm 'f may be nected with one of the conductors ll of a direct mamtained i th normalmanner thereon current output line having the second conductor 40 1 It is, therefore, among the objects of the present thereof connected with the'neutrel Pints of invention to'provide an electric current convertwindings a and 9 through an interphase trans m system employing an interphase transformer, former l9. Interphase transformer I9 comprises the operation. of which is not :arfiectedby 6181 two windings I! and I8 severally connecting conturbances Occuring in the system ductor-Hi .with the neutral points of windings 8 4 5., a v and '9 respectively and each comprising three {2332K5:113;f gf f g ii fi e fe to phase'displaced sectionslla, l'lb, I10 and IM, lab p l 9 gsys pk and..|8c, respectively. Such windings are asploying an interphase transformer, the operation g semblediin'inductive relation with the phase disc! which 1s not affected by changes in the current placed sections, a Star connected winding 2| system J' thereby- V supply suchflwinding with voltages in proper .Another object or h -p ent invent on is to phase relation with .the voltages of windings a provide an electric currentconverting system emand ,9, asfor instance, by energizing winding 2| 1 ploying an interphase transformer in which an from'the terminals of winding 8. 'Windings I1, alternating current magnetization is maintained I81 and 2| are arranged on a three phase core distribution. between h several m i sd the energized from line 6 in any suitable manner to 0 structure 22 which is preferably of the type entering into the construction of transformers of the shell type as illustrated in Fig. 2.

The operation of the system will be understood from the following explanation. Assuming line 6 to be energized, winding I which is energized therefrom, induces voltages in windings 8 and 9 which constitute a six phase system of voltages. Winding 2| receives three phase voltages and draws, from line 5, magnetizing current having fundamental and harmonic components (other than triple harmonic components) to magnetize core 22 and thereby induce, in windings l1 and I8, three phase voltages of proportionate magnitudes. As a result of the delta or polygon connection of windings i! and i8, however, such three phase voltages cancel each other in the circuits of such windings and do not appear at the terminals thereof. Such voltages are, therefore, without effect and need not be further considered.

Upon connection of current consuming devices" (not shown) across line H, l6, device |2 will de-' liver current to such devices, such current flowing in equal amounts through windings Hand IS in the absence of any cause tending to disturb the distribution of such currents. Under such conditions, and if the value of the load current is at least equal to the so-called critical load which is the minimum load required to cause opera ion of the interphase transformer, windings 8 and 9 will carry current simultaneously at every instant as a result of the arrangement of windings l1 and |8 on a common magnetic core. Interphase transformer l9 then maintains the voltage of line l4, [6 at the average value of the rectified voltages of the windings 8 and 9, the difference of the instantaneous voltages of windings 8 and 9 appearing as a third harmonic voltage across windings ll and IS. A common third harmonic flux corresponding to such third harmonic voltage then links with windings 2|, I! and I8 but such flux component does not disturb the operation of winding 2| because the third harmonic voltage components induced by such flux component in the several sections of winding 2| cancel each other between terminals thereof. The magnetizing current producing such third harmonic flux component is supplied by the alternating current components of the currents in windings I! and 53; such components are in phase opposition but their effects are additive due to the method of connection of windings l1 and I8. The greater part of the load current constitutes direct current components likewise flowing through windings H and l 8, but such components tend to magnetize the core 22 in opposite directions and are, therefore, without effect on the magnetization of such core, provided that such components remain equal in magnitude. Under such conditions, interphase transformer 9 therefore operates in the same manner as interphase transformers known in the art.

If the currents flowing through windings I1 and 8 become unequal for any reason, the magnetizing effects of the direct current components thereof on the core 22 will no longer cancel each other and core 22 is subjected to a direct current magnetization which is generally sufficient to cause magnetic saturation thereof. The magnetic permeability of such core then is very much reduced and, in order to maintain therein the alternating current flux component necessary for the normal operation thereof, an alternating current magnetizing component would be required which would generally be considerably larger than the alternating current components obtainable from the load currents in windings l1 and 18. In the absence of winding 2|, the alternating current flux component in core 22 would therefore become considerably reduced and interphase transformer I9 would become partly or totally ineffective. As a result of the direct current magnetization of core 22 and of the star connection of the sections of winding 2|, winding 2| draws, from line 6, an increased amount of magnetizing current component of fundamental frequency, as is well known in the art, to produce a third harmonic flux component in core 22. Winding 2| is preferably so designed that such flux component is substantially equal to the flux component normally produced by the flow of load current, thereby causing interphase transformer l9 to continue to operate in the normal manner thereof.

Winding 2| is therefore operable to contribute to the alternating current'excitation of core 22 upon accidental direct current magnetic saturation thereof, by cooperating with the currents flowing through the windings of the interphase transformer to excite the core thereof upon occurrence of unbalances in the distribution of such currents. Winding 2| thus maintains the normal operation of interphase transformer l8 upon occurrence of such unbalances;

In the above explanation it was assumed that the alternating current flux produced in core 22 by energization of winding 2| alone was insufficient to bring such core to magnetic saturation. Winding 2| may, however, also'be so designed that the alternating current flux produced there by in core 22 reaches the saturation point. As is well known, winding 2| then draws, from line i, an increased magnetizing current component of fundamental frequency whereby the alternating current flux of core 22 receives a third harmonic flux component in addition to the fundamental component thereof. The flow of a third harmonic flux component in core 22 is thus adequately provided by winding 2| and is, therefore, independent of conditions in windings l1 and I8. Winding 2| will, therefore, maintain the operation of interphase transformer H! as well during normal operation as upon occurrence of unbalances in the distribution of current between windings l1 and I8. In addition, when the load current decreases below the minimum value at which such currents would suffice for alone maintaining core 22 magnetized, the so-called critical value, winding 2| maintains core 22 magnetized and interphase transformer I9 continues to operate in the normal manner thereof. windings 8 and 9 then continue to carry current simultaneously at every instant and the voltage of line I4, I6 remains substantially constant, wh'ereasin the absence of winding 2| the voltage of line ll, I6 would gradually rise to the value corresponding to the value attained in the absence of interphase transformer I9 as the load current decreasesto zero.

Although but one embodiment of the present invention has been illustrated and described, it will be apparent to those skilled in the art that various changes and modifications may be made therein without departing from the spirit of the invention or from the scope of the appended claims.

It is claimed and desired to secure by Letters Patent:

1. In combination, an alternating current line, a transformer having a primary winding connected with said line and having a plurality of secondary windings each provided with a neutral point, electron discharge means connected with said secondary windings, an interphasetransformer having windings connected between the neutral points of said secondary windings, a direct current line connected with said interphase transformer and with said discharge means, and means for maintaining the operation of said interphase transformer upon occurrence of unbalances in the distribution ofcurrent between said secondary windings.

2. In combination, an alternating current line, a transformer having a primary winding connected with said line and having a plurality of secondary windings each provided with a neutral point, electron discharge means connected with said secondary windings, an interphase transformer having windings connected between the neutral points of said secondary windings, a direct current line connected with said interphase transformer and with said discharge means, and

meansresponsive to the occurrence of unbal-p ances in the distribution of current between said secondary windings and cooperating with the current flowing through the windings of said interphase transformer to excite the latter.

3. In combination, an alternating current line, a transformer having a primary winding connected with said line and having a plurality of secondary windings each provided with a neutral point, electron discharge means connected with said secondary windings, a magnetically saturable core structure, an interphase transformer having windings connected between the neutral points of said secondary windings and arranged on said core structure, a direct current line connected with said interphase transformer and with said secondary windings each provided with a neutral point, electron discharge means connected with said secondary windings, a direct current line connected with said discharge means, a magnetically saturable core structure, an interphase transformer having aplurality of windings each comprising a plurality of phase displaced sections serially connected in polygon connection between said direct current line and the neutral points of said secondary windings and arranged on said core structure, and a winding comprising a plurality of phase displaced star connected sections arranged on said core structure in inductive relation with the windings of said interphase transformer and energized from said altenating current line.

5. In combination, an alternating current line, a transformer having a primary winding connected with said line and having a plurality of secondary windings each provided with a neutral point, electron discharge means connected with said secondary windings, an interphase transformer having windings connected between the neutral points of said secondary windings, a direct current line connected with said interphase 6. In combination, an alternating. current line a transformer having a primary winding connected with said line and having a plurality of' secondary windings each provided witha neutral point, electron discharge means connected with said secondary windings, an interphase transformer having windings connected between the neutral points of said secondary windings, a direct current line connected with said interphase transformer and with said discharge means, and means for maintaining the operation of said interphase transformer upon occurrence of unbalances in the distribution of current between said secondary windings and for maintaining the voltage of said direct current line at a substantially constant value at loads below a predetermined value. 7 I

'7; In combinatioman alternating current line, a transformer having a primary winding connected with said line and having a plurality of secondary windings each provided with a neutral point, electron discharge means connected with said secondary windings, a direct current line connected with said discharge means, an interphase transformer having a plurality of windings each comprising a plurality of phase displaced sections serially connected in polygon connection a between said direct current line and the neutral points of said secondary windings and arranged on a magnetically saturable core structure, and a winding comprising, a plurality of phase displaced star connected sections arranged on said core structure in inductive relation with the windings of said interphase transformer and energized from said alternating current line to produce alternating current magnetic saturation of said core.

HAROLD WINOGRAD. 

